2 A B C D E F G H I K L M N O P R S T U V W

exit pupil

= image of the physical iris of a lens, as seen through the (image side) lens elements.
(C) Wikipedia

exit pupil

Here we also see the Chief Ray Angle = CRA between the chief ray and the optical axis. Some sensors like for example from E2V accept only angles between 5 and 20 degrees, say != zero.

If (image side) CRA==0, we call the lens “image side telecentric”.